Sebastian Elser, Prof. Ben Moore and Dr. Joachim Stadel of the University of Zurich, Switzerland, in cooperation with Ryuji Morishima of NASA's Jet Propulsion Laboratory, tried to estimate how common Earth-Moon planetary ...

Hot on the heels of confirming one Kepler planet, the Hobby-Eberly Telescope announces the confirmation of another planet. Another observatory, the Nordic Optical Telescope, confirms its first Kepler planet as well, this ...

(PhysOrg.com) -- Using the super-sharp radio "vision" of astronomy's most precise telescope, scientists have extended a directly-measured "yardstick" three times farther into the cosmos than ever before, an achievement with ...

(PhysOrg.com) -- Astronomers over the past decade have made remarkable progress in the study of extrasolar planets; over 500 distant worlds are now confirmed. Meanwhile, as this active research community continues to discover ...

Two movies derived from images taken by the two cameras aboard NASA's EPOXI mission spacecraft show comet Hartley 2 is, as expected, quite active, and it provides information on the nucleus's rotation. The spacecraft has ...

Extrasolar planet

An extrasolar planet, or exoplanet, is a planet beyond our Solar System, orbiting a star other than our Sun. As of June 2009[update], 353 exoplanets are listed in the Extrasolar Planets Encyclopaedia. The vast majority have been detected through radial velocity observations and other indirect methods rather than actual imaging. Most announced exoplanets are massive gas giant planets thought to resemble Jupiter, but this is a selection effect (bias) due to limitations in detection technology. Projections based on recent detections of much smaller worlds suggest that lightweight, rocky planets will eventually be found to outnumber extrasolar gas giants.

Extrasolar planets became a subject of scientific investigation in the mid-19th century. Many astronomers supposed that such planets existed, but they had no way of knowing how common they were or how similar they might be to the planets of our Solar System. The first confirmed radial velocity detection was made in 1995, revealing a gas giant planet in a four-day orbit around the nearby G-type star 51 Pegasi. The frequency of detections has tended to increase on an annual basis since then. It is estimated that at least 10% of sun-like stars have planets, and the true proportion may be much higher. The discovery of extrasolar planets sharpens the question of whether some might support extraterrestrial life.

Currently Gliese 581 d, the fourth planet of the red dwarf star Gliese 581 (approximately 20 light years from Earth), appears to be the best example yet discovered of a possible terrestrial exoplanet that orbits within the habitable zone surrounding its star. Although initial measurements suggested that Gliese 581 d resided outside the so-called "Goldilocks Zone", additional measurements place it firmly within.